1. Field of the Invention
The present invention relates to a method for the unambiguous allocation of useful data transmitted between a first communication local end and a second communication local end to a specific originator, whereby a hash result that is subjected to a crypto algorithm is formed in addition to the useful data.
2. Description of the Prior Art
Methods of the type described above are also known in the art by the rubric of "electronic signatures". Generating an electronic signature is based on the utilization of an asymmetrical RSA transformation method. The information to be signed is thereby compressed to a fixed length according to a system-wide, public method, what is referred to as a hash method. The result of this compression is subsequently further processed with the private RSA code of the originator. For the output information transmitted in clear text, the signature can be verified at the receiver or at a special system entity, in that the production of the signature with the public key of the originator is reduplicated according to the same method. The authenticity of the document is checked by comparing the results. When the result of the check is positive, it is assured, first of all, that the document arrives from a specific originator and, secondly, that no further modification was undertaken after the signing of the document.
The production of such a digital signature in communication in networks previously occurred in the terminal equipment of the signatory. This is then referred to as a decentralized method. Only the pairs of codes employed are centrally generated and administered, whereby this involves a public key code and a private key code as a result of the asymmetrical coding method. Security problems arise in the manipulation of the private key code to be protected, particularly given the utilization of the known method with personal computers (PCs). The crypto methods being employed (for example, RSA) require a certain computer size, as a result whereof an accommodation in standardized processor chip cards presents technological difficulties at the present time.
A symmetrical code with processor chip cards has already been realized. However, an asymmetrical coding is better suited for networks because of the less-involved key management involved therewith. Here, also, however, the processor chip card technology has not yet been adequately developed.
At present, the utilization of the crypto algorithm for operating the digital signature therefore usually occurs within an apparatus separated from the PC. Since this apparatus is connected to the actual PC via a line, there is here the possibility of inadmissible manipulations.
A further disadvantage is comprised in that the personal key code of the user is located on his processor chip card and, therefore, the problem of protecting this card against unauthorized access arises.